The present invention relates to improvements in or relating to a binocular's focus or zoom adjusting knob.
For instance, according to U.S. Pat. No. 4,066,329, as shown schematically in FIG. 1 a focus adjusting knob 5 has a pair of generally flattened platforms 4, 4' arranged to be contacted by the fingers of a user's hands. This known binocular includes a pair of telescopes 3, 3' which are linked with each other by way of arms 2, 2 and are rotatable along a center shaft 1. And the focus adjusting knob 5 is coupled to a pair of ocular lenses 6, 6' through cam means 8 for rapid, short-stroke focus adjustment. The focus adjusting knob 5 is a unique structure in view of its flattened surface. The focus adjusting knob 5 is moved in a treadle or seesaw way with the user's fingers, thereby a smooth focus adjustment is obtained.
When a person who has a narrow interpupillary space between his or her two eyes uses the binocular of the above structure, the position of the adjusting knob 5 becomes higher in relation to the two telescopes 3, 3' as shown in FIG. 1c. In this case, the flattened platforms 4, 4' are contacted by the fingers, thereby the adjusting knob being operable.
On the other hand, for a person who has a wider interpupillary space, the position of the adjusting knob 5 becomes relatively lower in relation to the top surface of the two telescopes 3, 3' as shown in FIG. 1b. As a result, it becomes not easy to press the two platforms 4, 4'. Namely, the two platforms 4, 4' must be contacted by the fingers in such a manner as to force them downwardly from the top surface of the two platforms 4, 4'. In other words, the fingertips are obliged to be extended to them, so that it is not easy to press them smoothly. In view of the above inconvenience, the present invention has been achieved.